Battery Charge Equalization via Selective Switching
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Solution Overview
Problem
Series-connected batteries in industrial applications often experience unbalanced charging due to differences in charging and discharging characteristics, leading to overcharge or undercharge issues, which can result in battery explosion or reduced lifespan, and existing charge equalization methods suffer from high energy loss, cost, or size constraints.
Innovation Solution
A battery system with a number of series-connected batteries and charge equalizers, where a control device determines SOC for each battery, connects those requiring equalization to charge equalizers, using a selective switch module to achieve charge balance, with the number of equalizers being less than the number of batteries to optimize charge equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive charge equalization approach with parallel resistors is used, then implementation cost is low, but energy loss is high and charge equalization capability is limited for high current batteries
Solution Approach 1:
The system divides the battery string into multiple groups, with each group containing one or more series-connected batteries. Each group is equipped with its own charge equalizer that can independently perform charge equalization on batteries within that group. This segmentation allows the system to achieve effective charge equalization across the entire battery string while using fewer charge equalizers than the total number of batteries, thereby reducing implementation cost while maintaining energy efficiency.
2Loss of energy
If active charge equalization approach with power electronics circuit is used for each battery, then energy efficiency is high and charge equalization for high current batteries is achieved, but implementation cost and device size increase
Solution Approach 1:
Each charge equalizer is designed to perform multiple functions: it can equalize charge for all batteries within its assigned group, and multiple charge equalizers can work cooperatively to handle the entire battery string. This multi-functionality allows the system to achieve high energy efficiency through active charge equalization while reducing the total number of charge equalizers needed, thereby lowering implementation cost compared to providing individual power electronics circuits for each battery.
3Productivity
If individual power electronics circuit is provided for each battery, then charge equalization capability for high current batteries is achieved, but device size and implementation cost increase
Solution Approach 1:
Multiple batteries that are series-connected and have similar charge characteristics are grouped together, and a single charge equalizer is assigned to handle charge equalization for all batteries within that group. This merging approach reduces the total number of charge equalizers needed, thereby reducing device size and implementation cost while maintaining adequate charge equalization capability for high current batteries through the coordinated operation of multiple charge equalizers.
Data Source
AI summary
A battery system has a battery module including a number M of series-connected batteries. The battery system is further provided with a number N (1<N≦M) of charge equalizers, each of which once connected to a battery, causes the battery to be charged and/or discharged to achieve charge equalization. A control device is configured to determine for each battery if it requires charge equalization based on a state of charge (SOC) of the battery, compare a number L of the batteries that require charge equalization and the number M, and based on the comparison result, cause the battery system to be shut down, or the one or more batteries that require charge equalization to be connected to corresponding charge equalizers. A selective switch module is used for connecting the one or more batteries that require charge equalization to corresponding charge equalizers, respectively.